Fixed in-place modifications to `data['fluxcov']` 	modified:   sncosmo/fitting.py
Fixed in-place modifications to `data['fluxcov']`
	modified:   sncosmo/fitting.py

sncosmo/sncosmo,sncosmo/sncosmo,kbarbary/sncosmo,sncosmo/sncosmo,dannygoldstein/sncosmo,kbarbary/sncosmo,dannygoldstein/sncosmo,kbarbary/sncosmo,dannygoldstein/sncosmo